2 files changed, 77 insertions, 20 deletions

diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 6a01ded615cd..fe59e18dbd5b 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -8,6 +8,7 @@
 
 #include <linux/acpi.h>
 #include <linux/bitmap.h>
+#include <linux/cpuhotplug.h>
 #include <linux/ctype.h>
 #include <linux/log2.h>
 #include <linux/memory.h>
@@ -29,6 +30,7 @@
 
 #define MISALIGNED_ACCESS_JIFFIES_LG2 1
 #define MISALIGNED_BUFFER_SIZE 0x4000
+#define MISALIGNED_BUFFER_ORDER get_order(MISALIGNED_BUFFER_SIZE)
 #define MISALIGNED_COPY_SIZE ((MISALIGNED_BUFFER_SIZE / 2) - 0x80)
 
 unsigned long elf_hwcap __read_mostly;
@@ -557,30 +559,21 @@ unsigned long riscv_get_elf_hwcap(void)
 	return hwcap;
 }
 
-void check_unaligned_access(int cpu)
+static int check_unaligned_access(void *param)
 {
+	int cpu = smp_processor_id();
 	u64 start_cycles, end_cycles;
 	u64 word_cycles;
 	u64 byte_cycles;
 	int ratio;
 	unsigned long start_jiffies, now;
-	struct page *page;
+	struct page *page = param;
 	void *dst;
 	void *src;
 	long speed = RISCV_HWPROBE_MISALIGNED_SLOW;
 
 	if (check_unaligned_access_emulated(cpu))
-		return;
-
-	/* We are already set since the last check */
-	if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_UNKNOWN)
-		return;
-
-	page = alloc_pages(GFP_NOWAIT, get_order(MISALIGNED_BUFFER_SIZE));
-	if (!page) {
-		pr_warn("Can't alloc pages to measure memcpy performance");
-		return;
-	}
+		return 0;
 
 	/* Make an unaligned destination buffer. */
 	dst = (void *)((unsigned long)page_address(page) | 0x1);
@@ -634,7 +627,7 @@ void check_unaligned_access(int cpu)
 		pr_warn("cpu%d: rdtime lacks granularity needed to measure unaligned access speed\n",
 			cpu);
 
-		goto out;
+		return 0;
 	}
 
 	if (word_cycles < byte_cycles)
@@ -648,19 +641,84 @@ void check_unaligned_access(int cpu)
 		(speed == RISCV_HWPROBE_MISALIGNED_FAST) ? "fast" : "slow");
 
 	per_cpu(misaligned_access_speed, cpu) = speed;
+	return 0;
+}
 
-out:
-	__free_pages(page, get_order(MISALIGNED_BUFFER_SIZE));
+static void check_unaligned_access_nonboot_cpu(void *param)
+{
+	unsigned int cpu = smp_processor_id();
+	struct page **pages = param;
+
+	if (smp_processor_id() != 0)
+		check_unaligned_access(pages[cpu]);
+}
+
+static int riscv_online_cpu(unsigned int cpu)
+{
+	static struct page *buf;
+
+	/* We are already set since the last check */
+	if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_UNKNOWN)
+		return 0;
+
+	buf = alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER);
+	if (!buf) {
+		pr_warn("Allocation failure, not measuring misaligned performance\n");
+		return -ENOMEM;
+	}
+
+	check_unaligned_access(buf);
+	__free_pages(buf, MISALIGNED_BUFFER_ORDER);
+	return 0;
 }
 
-static int __init check_unaligned_access_boot_cpu(void)
+/* Measure unaligned access on all CPUs present at boot in parallel. */
+static int check_unaligned_access_all_cpus(void)
 {
-	check_unaligned_access(0);
+	unsigned int cpu;
+	unsigned int cpu_count = num_possible_cpus();
+	struct page **bufs = kzalloc(cpu_count * sizeof(struct page *),
+				     GFP_KERNEL);
+
+	if (!bufs) {
+		pr_warn("Allocation failure, not measuring misaligned performance\n");
+		return 0;
+	}
+
+	/*
+	 * Allocate separate buffers for each CPU so there's no fighting over
+	 * cache lines.
+	 */
+	for_each_cpu(cpu, cpu_online_mask) {
+		bufs[cpu] = alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER);
+		if (!bufs[cpu]) {
+			pr_warn("Allocation failure, not measuring misaligned performance\n");
+			goto out;
+		}
+	}
+
+	/* Check everybody except 0, who stays behind to tend jiffies. */
+	on_each_cpu(check_unaligned_access_nonboot_cpu, bufs, 1);
+
+	/* Check core 0. */
+	smp_call_on_cpu(0, check_unaligned_access, bufs[0], true);
+
+	/* Setup hotplug callback for any new CPUs that come online. */
+	cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "riscv:online",
+				  riscv_online_cpu, NULL);
+
+out:
 	unaligned_emulation_finish();
+	for_each_cpu(cpu, cpu_online_mask) {
+		if (bufs[cpu])
+			__free_pages(bufs[cpu], MISALIGNED_BUFFER_ORDER);
+	}
+
+	kfree(bufs);
 	return 0;
 }
 
-arch_initcall(check_unaligned_access_boot_cpu);
+arch_initcall(check_unaligned_access_all_cpus);
 
 void riscv_user_isa_enable(void)
 {
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index d69c628c24f4..d162bf339beb 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -247,7 +247,6 @@ asmlinkage __visible void smp_callin(void)
 	riscv_ipi_enable();
 
 	numa_add_cpu(curr_cpuid);
-	check_unaligned_access(curr_cpuid);
 	set_cpu_online(curr_cpuid, 1);
 
 	if (has_vector()) {